Apparatus for filling and sealing alkali metal electrode containers for alkali metal energy conversion devices and method of filling alkali metal electrode containers for alkali metal energy conversion devices

ABSTRACT

The present invention discloses an apparatus with entry, filling and sealing, and exit chambers through which a carriage holding alkali metal containers may be transferred. The drive for the carriage in each chamber is cantilevered to facilitate transfer between chambers, and lateral movement of the carriage with the respect to the direction of transfer is restricted in the filling and sealing chamber. A method of filling containers with molten alkali metal is also disclosed in which the ambient gas pressure is reduced and then raised to reduce quantities of unwanted gas in the alkali metal.

BACKGROUND OF THE INVENTION

The present invention is concerned with apparatus for filling andsealing alkali metal electrode containers for alkali metal energyconversion devices. This invention also relates to a method of fillingalkali metal electrode containers for alkali metal energy conversiondevices with alkali metal.

Such devices employ an alkali metal as one or sometimes both of theelectrodes in a cell including a separator, or electrolyte, between theelectrodes, formed of a solid ceramic material which is electronicallyinsulating but conductive to cations of the alkali metal.

A particular example of such devices is the sodium sulphur cell whichemploys liquid sodium as the anode of the cell and liquid sulphur/sodiumpolysulphide material as the cathode, the two being separated by a solidelectrolyte of beta alumina.

Sodium sulphur cells for experimental purposes have been made in smallquantities and it is very readily possible to fill the sodium reservoiror container of the cell by carrying out the filling operation in aclosed chamber filled with a suitable inert gas, the cell being sealedbefore removal from the chamber. The entire operation is carried out ata temperature substantially in excess of the melting point of sodium,typically 150° C.

However, such a technique is not suitable for quantity production ofcells. Since the cells must be heated within the chamber prior tofilling and then allowed to cool again. Furthermore, once the filledcells have cooled, the chamber must be broached to remove the cells andfor the insertion of a fresh batch, whereupon the atmosphere in thechamber must be purged of any air before the next batch is heated andfilled.

GB-A-2061598 describes a method and apparatus for filling sodium sulphurcells which avoids some of these difficulties. In the describedarrangement, each sodium container or reservoir is provided with an openended metal filler tube protruding from the container. Empty containersare heated progressively and presented to a sodium filling head whilstin air at atmospheric pressure. The filling head is specially designedto seal around the filler tube of the sodium container, evacuate airfrom within the sodium container before feeding sodium into theevacuated container. The filling head is then designed to pinch off themetal tube to seal the container before breaking the seal made with thefiller tube. To facilitate this operation, it is usually necessary forthe filler head to have a feed tube which can be inserted down throughthe filler tube of the cell into the interior of the sodium container soas to feed sodium directly into the container. The requirement for thefilling head to seal to the filler tube of the sodium container alsorenders the design of the filling head relatively complicated as can beappreciated from the above referred specification.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, apparatus for fillingand sealing an alkali metal electrode container for an alkali metalenergy conversion device comprises intercommunicating entry, filling andexit chambers, entry and exit doors which are closable to hermeticallyseal the filling chamber from the entry and exit chambers respectively,hermetically sealable entry and exit hatches to the entry and exitchambers respectively, interlock means to permit opening of said entryor exit hatch only when the respective said entry or exit door isclosed, transfer means operable to transfer an electrode container to befilled and sealed successively from the entry chamber to the fillingchamber and, when filled and sealed, from the filling chamber to theexit chamber, vacuum means arranged for independently controlling theatmosphere in each of the entry, filling and exit chambers to providepredetermined pressures of inert gas in said chambers, heating meansarranged for independently controlling the temperatures in at least saidentry and filling chambers, and filling and sealing means arranged tofill and seal said electrode container in the filling chamber, the saidtransfer means comprising a carriage arranged to hold at least one saidelectrode container, and respective drive means in each of said chambersguiding and propelling the carriage in the respective chamber, therespective drive means in adjacent communicating chambers being adaptedto co-operate in supporting and propelling the carriage from one saidchamber to the next through the open door between the chambers, thecarriage having sufficient length in the direction of transfer to ensurefull guided supporting engagement with one drive means is retainedduring transfer at least until the carriage engages the next drivemeans.

By this arrangement, the simplicity is obtained of filling the cells inan evacuated, or inert gas filled, heated chamber, so as to avoid theneed for a filling head to make individual seals with the sodiumcontainers to be filled. At the same time, the inefficiency ofsuccessively re-evacuating and heating the filling chamber is avoided byproviding the intercommunicating entry and exit chambers. The entrychamber can then be used for heating and purging the cells ready fordelivery to the filling chamber as soon as this has completed a previousfilling and sealing operation. At the same time, the exit chamber canreceive newly filled and sealed cells immediately from the fillingchamber without compromising its inert atmosphere or operatingtemperature. The cells can then be cooled down and delivered toatmosphere from the exit chamber. The interlock means ensure that theintegrity of the atmosphere in the filling chamber is maintained and thetransfer means enable single electrode containers or batches ofcontainers to be transferred between the various chambers at appropriatetimes in the process.

Conveniently, each drive means is adapted to provide cantilever supportfor the carriage during transfer, until engagement with the followingdrive means and after disengagement from a preceding drive means.

In an embodiment, the drive means in the filling chamber includes alength of rail for engagement on opposite sides of the rail by opposedpairs of rollers on the carriage, the end of the rails adjacent theentry door being tapered to facilitate engagement of the rail betweensaid pairs of rollers during transfer. Preferably, the said opposedpairs of rollers are arranged to substantially restrict the movement ofthe carriage in a direction perpendicular to the axis of the drivemeans. Conveniently, the movement of the carriage is not so restrictedin the entry and exit chambers, there being some such movement allowed.This arrangement facilitates engagement of the opposed pairs of rollerswith the said length of rail when the carriage is transferred to thefilling chamber.

Using the form of transfer means described above, the carriage may beadapted to hold said electrode container at a predetermined position onthe carriage and the drive means in the filling chamber may be arrangedto convey the electrode container on the carriage between respectivefilling and sealing stations within the filling chamber, the apparatusincluding inter-engagable locating means on the carriage and in thefilling chamber actuatable to locate the electrode chamber accuratelyrelative to the filling and sealing means in the filling and sealingstations respectively. Said inter-engagable locating means may comprisea locating pin mounted either on the carriage or in the filling chamberto be longitudinally movable on actuation to engage in a correspondingaperture in the filling chamber or on the carriage respectively. Eitherthe locating pin or said aperture or both may be tapered to assistpositive engagement between the pin and aperture.

Preferably there is a single said locating pin and a respective saidcorresponding aperture for each of the filling and sealing stations.Instead, there may be at least two locating pins mounted in the fillingchamber arranged for engaging successively in a common aperture in thecarriage to locate the electrode container firstly at the fillingstation and secondly at the sealing station.

In a preferred embodiment the apparatus may include guide means in thefilling chamber for supporting and guiding the electrode containerbetween respective filling and sealing stations in the filling chamber,and lifting means actuatable to lift the guide means and the electrodechamber supported thereon into operative engagement with the filling andsealing means.

In accordance with a further aspect of the invention, a method offilling alkali metal electrode containers, for alkali metal energyconversion devices, each container holding solid material, with analkali metal having a large wetting angle to the solid material,comprises the steps of filling a said container with gas which is inertto the alkali metal; pumping a predetermined quantity of alkali metalinto the container; reducing the pressure of said gas in the containerand then raising the pressure of the gas to increase the wetting of thesolid material by the alkali metal.

In particular, the container may be the sodium compartment of asodium-sulphur cell; the alkali metal may be sodium and the solidmaterial may be particulate aluminium typically used as a getteringagent to maintain the sodium free of impurities. The method of thepresent invention allows for the effective wetting of the solid materialand substantially reduces the quantities of gas present in the alkalimetal.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of the present invention will now be described in more detailwith reference to the accompanying drawings in which:

FIG. 1 is a schematic diagram of filling and sealing apparatus embodyingthe invention and particularly adapted for filling the sodium containerfor a sodium sulphur cell;

FIG. 2 is a plan view partly in cross-section of a carriage for carryingten sodium containers for filling and sealing in the apparatusillustrated in FIG. 1;

FIG. 3 is an elevational view from one end, partially in cross section,of the carriage of FIG. 2;

FIG. 4 is a cross-sectional view of a typical sodium container for asodium sulphur cell and which may be filled and sealed by the apparatusillustrated in these drawings;

FIG. 5 is a side view in elevation of the entry chamber of the apparatusillustrated in FIG. 1, showing the drive means for guiding andpropelling the carriage of FIGS. 2 and 3 within the entry chamber.

FIG. 6 is a cross-sectional view of the drive means of FIG. 5 from oneend taken along the line A--A in FIG. 5;

FIG. 7 is a side view in elevation illustrating the transfer of acarriage from the drive means of the entry chamber to the drive means inthe filling chamber;

FIG. 8 is an elevational view from one end, partially in cross-section,of the drive means in the filling chamber;

FIG. 9 is a sectional view in elevation through the entry chamberproviding a view of the entry door to the filling chamber;

FIG. 10 is a cross-sectional view of the entry door of FIG. 9 from oneside;

FIG. 11 is a view in elevation from one side of the filling chamberillustrating in particular the filling head and the sealing stationwithin the chamber;

FIGS. 12 and 13 are more detailed illustrations of an assembly forplacing the current collector into the aperture in the sodium containerready for sealing of the container;

FIGS. 14 and 15 are views of the filling chamber from one side and oneend respectively and particularly illustrating the mechanism for liftingthe guide rail within the filling chamber to bring the sodium containersin the carriage mounted thereon into engagement with the filling,current collector locating and sealing heads in the chamber;

FIG. 16 is a detailed view of the filling chamber from one endillustrating, partially in cross-section, the mechanism for actuatingthe locating pins to locate the carriage within the filling chamberaccurately relative to the filling, current collector locating andsealing heads;

FIG. 17 is a detailed view in cross section of the carriage assemblyillustrating the aperture therethrough for reception of the locatingpin; and

FIG. 18 is a schematic diagram of the vacuum and argon supply system forthe apparatus.

DETAILED DESCRIPTION

Referring to FIG. 1, the apparatus is formed of a three chamber pressurevessel. Each chamber of the vessel is generally cylindrical in shape andthe three chambers are arranged coaxially with the two outer chambersbeing somewhat smaller in diameter and shorter than the central chamber.From left to right in FIG. 1, the chambers comprise an entry chamber 1 afilling and sealing chamber 2 and an exit chamber 3. An entry door 4enables communication between the entry chamber 1 and the fillingchamber 2, and an exit door 5 similarly enables communication betweenthe filling chamber 2 and the exit chamber 3. The doors 4 and 5 enablethe filling chamber 2 to be sealed hermetically relative to the entrychamber 1 and the exit chamber 3.

An entry hatch 6 provides access to the entry chamber 1 and similarly anexit hatch 7 provides access to the exit chamber 3. The hatches 6 and 7also may be closed to hermetically seal the respective entry and exitchambers 1 and 3.

Within each of chambers 1, 2 and 3 there are provided respective drivemeans 8, 9 and 10 for guiding and propelling forward in the chamber acarriage 11 on which may be mounted a number of sodium containers 12 tobe filled and sealed in the apparatus.

As will be described in further detail later herein, the drive means 8,9 and 10 and the carriage 11 are arranged so that the carriage 11 can bepropelled from the entry chamber 1 into the filling chamber 2 when theentry door 4 is open, with the carriage 11 remaining supported andpropelled forward by the drive means 8 in the entry chamber 1 until itis fully engaged on the drive means 9 in the filling chamber, so that itcan then be drawn by the drive means 9 from the entry chamber completelyinto the filling chamber. Similarly, drive means 9 in the fillingchamber 2 co-operates with drive means 10 in the exit chamber fortransferring the carriage from the filling chamber to the exit chamberwhen required. Within the filling chamber 2, drive means 9 propels thecarriage 11 between a filling station 13 at which the containers 12 canbe filled with sodium, and a two position sealing station for sealingthe filled container. The sodium containers are presented for fillingwith only a small aperture in the lid of the container and the firststage of the sealing operation comprises inserting into this aperturethe usual current collector for the sodium electrode. This is done at acurrent collector insertion station 14, and then the filled container ismoved along by the drive means 9 to a welding station 15 at which thecurrent collector is welded into the aperture in the container so as toseal the container.

Further details of the filling and sealing operations within the fillingchamber 2 will be given later herein.

The entry chamber 1 and filling chamber 2 also include heaters 16 and 17respectively, shown in the diagram schematically. These heaters may beformed as electrically powered infra-red heaters suitably positionedwithin each chamber to heat up and maintain the temperature of thecontainers throughout the filling and sealing operations. It will beappreciated that the sodium is delivered to each sodium container whilstin molten state and it is therefore essential to keep the containersubstantially above the melting point of sodium metal.

Vacuum means, 18, 19 and 20 are provided also for separately evacuatingand controlling the atmosphere within each of the chambers 1, 2 and 3.The filling and sealing operation within the filling chamber 2 isconducted in an atmosphere of inert gas, typically argon and provisionis made for purging air from the entry chamber 1 after opening the hatch6 to supply a fresh batch of sodium containers for filling. Vacuum means20, on the other hand, permits the pressure in the exit chamber 3 to beequalised with atmospheric prior to opening the exit hatch 7 to removedfilled and sealed containers from the chamber. After resealing thechamber 3, the vacuum means 20 also purges any air from the chamber 3.

The entry and exit doors 4 and 5 of the filling chamber 2 are remotelyactuated to open and close the doors, by means of pneumatic cylinders 21and 22. The doors 4 and 5 are clamped into position when closed toprovide hermetic seals, by respective mechanisms each actuating by aplurality of further pneumatic cylinders of which one only isillustrated in FIG. 1 and identified by the reference numerals 23 and24.

The entry and exit hatches 6 and 7, once unlocked, can be physicallyopened and shut by hand. However they are each locked in the closedposition by respective groups of pneumatic cylinders of which again onlyone is shown in each case indicated by reference numerals 25 and 26.

All operations of the apparatus illustrated in FIG. 1 are controlledfrom a central control unit indicated schematically in the drawing bythe box 27. In particular, each of the pneumatic valves controlling thelocking and operation of the doors 4 and 5 and hatches 6 and 7 isremotely controlled from the control unit 27. The control unit 27 isarranged to provide an interlock so that the locks on the entry hatch 6cannot be released by means of the pneumatic cylinders 25 unless theentry door 4 to the filling chamber 2 is in the closed position (ascontrolled by pneumatic cylinder 21) and is clamped in place by means ofthe cylinders 23. Similarly, the locks on the exit hatch 7 cannot bereleased by means of the cylinders 26 unless the exit door 5 of thefilling chamber 2 is in the closed position (as controlled by cylinder22) and is clamped in place by means of the cylinders 24.

In this way, the integrity of the atmosphere within the filling chamber2 is maintained irrespective of ocassional opening of the hatches 6 and7 for delivery and withdrawal of batches of sodium containers.

Referring now to FIGS. 2 and 3, the carriage 11 in which a plurality ofsodium containers can be transported through the pressure vessel of FIG.1 is illustrated in more detail. A typical form of sodium containerwhich may be filled by the apparatus is illustrated in FIG. 4. Thecontainer comprises a cup 30 of solid electrolyte material, typicallybeta alumina. A lid 31 of electrically insulating alpha alumina isglazed to the open end of the cup 30. This unit, comprising the cup 30and the glazed on lid 31 forms the container to be filled with sodiumand subsequently sealed. The container is supplied to the fillingapparatus with a small aperture 32 through the centre of the lid 31. Ametal washer 33 is fastened and sealed to the outer surface of the lid31, typically by thermocompression bonding, so as to surround theaperture 32 as shown in the drawing. In the filled and sealed sodiumcontainer, a pin 34, forming a current collector for the sodiumelectrode, is inserted through the aperture 32 so as to make contactwith sodium 35 within the container and is then welded to the washer 33so as to form an hermetic seal completely closing the sodium container.

When the container is supplied to the sodium filling apparatus forfilling and sealing, the pin 34 is not inserted in the aperture 32 andthe sodium metal is delivered through this aperture within theapparatus. Commonly, a quantity of dry particulate filler material maybe put into the sodium container before filling with sodium. This dryparticulate material may for example comprise aluminium flake or powderand is desirable within the sodium electrode compartment of thecompleted sodium sulphur cell, because it provides a "gettering"function purging impurities from the sodium within the cell duringoperation of the cell. The particulate aluminium material is put intothe container before the container is delivered for sodium filling inthe sodium filling apparatus.

Referring again to FIGS. 2 and 3, the illustrated carriage can hold tensodium containers for processing as a single batch through the fillingapparatus. The carriage comprises an upper plate 40 in which there are11 circular apertures 41, as shown in FIG. 2, for receiving the cups 30(not shown in FIG. 2) of sodium containers to be filled. The centralaperture 42 of the apertures 41 is not used to receive a container forfilling but is a blank position having a dummy container used fortemperature monitoring during the processing through the fillingapparatus.

The upper plate 40 is held spaced from a lower platform 43 by means of aplurality of stanchions 44, 45. Along one side of the row of apertures41, stanchions 44 are provided, one for each aperture as shown in FIG.2, though only five of the stanchions 44 include threaded portionsextending through the upper plate 40 and receiving nuts 46 securing theplate 40 to the stanchion. Each of the stanchions 44, except thatadjacent the central dummy aperture 42, are axially drilled from theirupper ends, visible through holes in the upper plate 40, so as toreceive the current collector pins 52 (FIG. 3) for the respective sodiumcontainer located in the adjacent aperture 41 of the top plate. Thus,not only are ten open sodium containers mounted in the respectiveapertures 41 in the top plate of the carriage, but also currentcollector pins for each of these containers are located immediatelyadjacent the respective containers.

The platform 43 of the carriage carries rollers (FIG. 3) for engaging onrails in the entry, filling and exit chambers of the filling apparatus.Rollers 47, 48, rotating about horizontal axis, are provided down bothsides of the platform 43 and these rollers engage between pairs ofvertically opposed rails provided in the entry and exit chambers as willbe described later herein. On the other hand, rollers 49, 50, rotatingabout vertical axis, are provided underneath the platform 43 to engageon opposite edges of an horizontally extending rail in the fillingchamber 2. Three sets of horizontally opposed rollers 49, 50 areprovided distributed along the length of the carriage.

Connections to the temperature sensor in the dummy container in aperture41 are taken to a connector block which is flush mounted in a portion 53of the platform 43 so as to present contact pads on the underside of theportion 53. Connections can be made to these pads, as will be describedlater, when the carriage is in any of the chambers 1, 2 or 3 of theapparatus so as to enable continuous monitoring of the temperature ofthe containers.

A tapered aperture 51 is provided extending upwards through the platform43 immediately beneath each container position, i.e. each aperture 41,42 in the upper plate 40. The aperture 51 through the platform 43 isadapted to receive a locating pin in the filling chamber 2 of theapparatus so as to locate the respective sodium container accuratelyrelative to the filling and sealing stations in the chamber.

Referring to FIG. 5, the carriage of FIGS. 2 and 3 is illustratedmounted on the transfer or drive means in the entry chamber 1 of theapparatus. The carriage is indicated in FIG. 5 by the reference number11 (corresponding to the reference used in FIG. 1), although for clarityonly the platform 43 of the carriage is shown in FIG. 5.

The entry hatch 6 to the entry chamber 1 is shown to the left hand sidein FIG. 5 and the carriage may be delivered from the entry chamberthrough the entry door (not shown) to the extreme right hand side inFIG. 5. The left hand end of the carriage is illustrated in FIG. 5 inlongitudinal section so that the rollers 49 on one side of the carriagecan be seen.

The manner in which the carriage 11 is mounted and guided within theentry chamber 1 is better illustrated in FIG. 6 which is across-sectional view taken along line A--A of FIG. 5. It can be seenfrom FIG. 6 that the carriage 11 is supported in the entry chamber bymeans of the laterally extending rollers 47 and 48. The rollers 49 and50 (FIG. 3) are not employed in the entry chamber and are omitted fromFIG. 6 for clarity. The rollers 47 and 48 engage between pairs of upperand lower rails 55 and 56, and 57 and 58 respectively. The rollers 48 toone side of the carriage 11 are circumferentially grooved to engagearound rails 57 and 58 to provide lateral support for the carriage 11.It will be appreciated that the spacing between the vertically opposedpairs of rails 55, 56 and 57, 58 is such as to enable the respectiverollers 47, 48 to rotate when engaging either the upper or the lowerrail. Thus there is a small amount of play to ensure that individualrollers do not engage both upper and lower rails simultaneously.

The carriage 11 is driven along the rails 55 to 58 by friction drivefrom a drive wheel 59. The drive wheel 59 is driven from an electricmotor (not shown in FIG. 6) via a drive train comprising a clutch andbrake assembly 60, rotary vacuum seal 61, flexible drive coupling 62 andmiter gears 63 and 64.

A further friction drive wheel corresponding to wheel 59 is providedtowards the other end of the rails 55 to 58 at the position indicated bythe axle bearing 65 in FIG. 5. This second drive wheel is connected by abelt drive to the axle of the first drive wheel 59. Pulley 66 of one endof the belt drive is illustrated in FIG. 6.

Position sensors are provided in entry chamber I for detecting thecarriage 11 as it is first introduced into the tracks 55 to 58, toinitiate forward drive once the carriage is fully engaged, andsubsequently to halt the drive when the carriage is fully drawn into thechamber. With reference to Figure, when the entry hatch 6 is fullyclosed and locked, the vacuum means 18 is operated to purge air from thechamber and provide a required pressure of argon. At the same time theheaters 16 are energised to begin heating the carriage and sodiumcontainers thereon up to the required temperature.

When the required temperature is reached, and the filling chamber 2 isready to receive the carriage, the entry door 4 is opened and transferof the carriage from the entry chamber 1 to the filling chamber 2 cantake place.

FIGS. 7 and 8 illustrate the drive means within the filling chamber 2and FIG. 7 in particular is a cross-sectional view showing carriage 11being transferred from the entry chamber 1 to engage in the drive means9 of the filling chamber 2. In FIG. 7, the entry chamber is shown on theright hand side and the filling chamber 2 on the left hand side.

In transferring the carriage through the door, the carriage is drivenforward by the drive means in the entry chamber so as to extend throughthe door from the drive means, still supported cantilever fashion by atleast two sets of rollers 47, 48, (only rollers 48 being visible in FIG.7) until rollers 49, 50 of the carriage engage on opposite side of anhorizontally extending rail 70 in the filling chamber 2. The rail 70 canbe seen in cross-section in FIG. 8 and has bevelled edges engaging inthe grooves in rollers 49 and 50 to provide both lateral and verticalguided support of the carriage.

In the transfer of the carriage from chamber 1 to chamber 2, drive ofthe carriage from chamber 1 is continued until the carriage has engageda first friction drive wheel 71 of the drive mechanism within thefilling chamber. Further, the rail 70 in chamber 2 and tracks 55 to 58in chamber 1 extend close enough to each other so that the carriage isfully supported cantilever fashion while being driven forward fromchamber 1 to engage the rollers 49, 50 on rail 70, and subsequently issupported by at least one pair of rollers 47, 48 in chamber 1 until asecond set of rollers 49, 50 have engaged rail 70 in chamber 2,whereupon the carriage is supported cantilever fashion from the rail 70as it is drawn fully into chamber 2.

Sensors detect that the carriage has progressed far enough into chamber2 to engage the first friction drive wheel 71 to operate the drive tocontinue drawing the carriage into the chamber.

As seen in FIG. 8, the drive in chamber 2 derives from an electric motor72 via gear box 73, flexible coupling 74, clutch and brake unit 75, asecond flexible coupling 76, a rotary vacuum seal 77, a further flexiblecoupling 78, and miter gears 79, 80.

Sufficient additional friction drive wheels corresponding to wheel 71are provided along the length of the rail 70 in chamber 2 to ensure thatthe carriage is engaged by at least one drive wheel throughout itsjourney through the chamber. The additional friction drive wheels aredriven by belt drives via pulleys corresponding to pulley 81 in FIG. 8.

The entry and exit doors 4 and 5 to the chamber 2 will now be describedin more detail with reference to FIGS. 9 and 10. In each case the dooris formed of a closure plate 85 which, when closed, covers an aperture86 through the bulkhead 87 between the filling chamber 2 and therespective outer chamber.

The closure plate 85 is mounted for sliding movement parallel to theplane of the aperture 86 between upper and lower rails 88 and 89 whichare fixed to the bulkhead 87. The closure member 85 is mounted on theserails 88 and 89 by means of rollers 90, 91 mounted in the closure plate85. The rollers 90, 91 are mounted so as to be axially slidable alonghorizontally extending axles 92, 93 which are perpendicular to the planeof the closure 85. Thus, the closure 85 has some limited movementtransverse to its plane and the plane of the aperture 86, thistransverse motion corresponding to sliding of the rollers 90, 91 alongthe axles 92, 93. Springs 94, 95 are fitted in the closure member 85 tourge the rollers 90, 91 away from the outer face 96 of the closure 85,thereby having the effect of urging the closure member 85 itself awayfrom its seating 97 around the aperture 86.

A resilient ring seal 98 is located in a circumferential groove in theclosure 85 so as to provide an hermetic seal between the closure and theseating 97 when the closure 85 is depressed against the biassing of thesprings 94, 95 against the seating. However, when not depressed againstthe seating, the springs 94, 95 assist in moving the closure membertransversely away from the seating 97, relieving the seal 98 so that theclosure 85 can then be slid open.

The sliding motion is given to the closure member 85 by a pneumaticcylinder mounted outside the pressure vessel and operating on a pistonrod 100 extending through a bellows seal 101. The piston rod 100 acts ona lever 102 which is pivoted at a lower end about pivot axis 103. Anupper end of the lever 102 has a slot 104 which engages a stud 105 fixedto the closure 85. Thus, operation of the pneumatic cylinder to draw thepiston rod 100 axially out of the pressure chamber through the seal 101,pivots the lever 102 and slides the closure 85 to open the door.

When the door is in the closed position, it must, as mentioned above, bedepressed, against the biassing of springs 94, 95 firmly against theseating 97 to compress the resilient ring seal 98. This depression ofthe closure member 85 is provided by a set of four toggle levers 106,107. Each lever 106, 107 is pivoted centrally from a bracket 108, 109fixed to the bulkhead 87. The levers 106, 107 pivot about axis which areparallel to the plane of the closure 85 and have cam following rollers110, 111 at the ends of the levers adjacent the closure 85. Theserollers 110, 111 engage cam surfaces or ramps 112, 113 fixed to theclosure 85, so that pivoting of the levers 106, 107 to move the rollers110, 111 outwards relative to the centre of the pressure vessel, causesthe rollers to ride up the ramps 112, 113 depressing the closure 85towards the seating 97.

The toggle levers 106, 107 are actuated by means of respective pneumaticcylinders 114 acting through piston rods 115, journalled to the ends ofthe levers 106, 107 opposite to the rollers 110, 111. For clarity, onlythe cylinders 114 operating the lower toggle levers 107 are shown in thedrawings.

In FIG. 10, the lower toggle lever 107 is shown in the released positionwhilst the upper toggle lever 106 is shown in the clamped positiondepressing the closure 85 against the seating 97. In practice all thetoggle levers will be operated simultaneously either to clamp theclosure 85 or to release it.

It will also be observed in FIG. 10 that the geometry of the togglelevers 106, 107 and ramps 112, 113 permit the toggle levers to bepivoted when clamping the closure member 85 slightly past the point ofmaximum depression of the closure 85 so as to provide a toggle action.The levers 106, 107 abut stops 116 when pivoted to the fully clampedposition and the geometry is such that outward pressure on the closure85 tends to push the toggle levers 106, 107 against the stops 116. Thus,the clamping effect can be released only by applying positive effort toretract the piston rods 115 from the clamped position.

FIG. 11 is a cross-sectional view of the filling chamber 2, showing thecarriage 11 (platform 43 only shown for clarity) mounted and guided onthe rail 70. A total of eleven sodium containers 120 (including thedummy container) are illustrated schematically as they would besupported on the carriage 11.

The filling chamber 2 includes a filling station including a fillinghead 121 arranged for feeding accurately controlled quantities of moltensodium into the cells 120 through the open apertures 32 (FIG. 4) in thelid of the container. In operation of the apparatus, the carriage 11 isdriven along the rail 70 after entering through the entry door (to theleft in FIG. 11) until the first container is correctly located relativeto the sodium filling head 121. An initial charge of sodium is then fedinto the cell before the carriage is driven on sufficiently to bring thenext container into the filling location. The filling operation proceedsuntil all ten containers have received an initial charge. It may then benecessary for a top up of sodium to be provided to each of thecontainers and so the carriage is driven back again to bring the firstcell back into alignment with the filling head.

When all containers have received the full charge of sodium, thecarriage 11 is driven to bring the first container into location under acurrent collector pin insertion head indicated generally at 122 in FIG.11. This pin insertion head 122 operates to pick up the currentcollector pin for the container from its position on the carriageimmediately adjacent the container as described with reference to FIGS.2 and 3. The pin is picked up from this location and inserted throughthe aperture 32 in the top of the container. The carriage 11 is thendriven forward to bring the next container into position for pininsertion.

A little further along the filling vessel 2 there is a welding head 123.When the fourth cell on the carriage 11 is brought into position for pininsertion under the insertion head 122, this also simultaneously bringsthe first container into position under the welding head 123. Thus, whenthe pin is being inserted into the fourth sodium container, the pinalready inserted in the first container is welded in place to the washer33 (FIG. 4) to seal the container. The operation is contined until allten containers on the carriage have been filled, had their pins insertedand subsequently welded to seal the container.

The detailed designs of the filling head 121 and the welding head 123are no concern of the present invention and no further description willbe given herein. However, further details of the pin insertion head 122are apparent from FIGS. 12 and 13. The insertion head 122 is mounted, asare the filling head 121 and welding head 123, on a frame assembly 124fixed within the filling chamber 2. A pair of axially movable androtatable shafts 125 and 126 extend down through a flange 127 of thefilling chamber 2 and also extend through the supporting frame 124. Thetwo shafts 125 and 126 are disposed side by side across the width of thechamber, so that FIG. 12 is a view of the insertion head looking alongthe length of the chamber from the welding head 123. Supported in afixed position from the frame 124 by means of a supporting rod 128 is aguide peg 129. This guide peg is positioned so as to provide a guidingaperture immediately over the aperture 32 of the sodium container intowhich the pin is to be inserted.

Attached to the lower end of the shaft 125 is a pick and place arm 130.The arm 130 has at one end 131 spring loaded "jaws" by which the arm canengage over the head of the current collector pin. In order to insert apin in a container, the shaft 125 is first rotated to the position asshown in dotted outline in FIG. 13, with the jaws at the one end 131 ofthe arm 136 precisely located over the head of the current collector pinmounted in the carriage. The shaft 125 is then moved downwards axiallyso that the jaws mechanically engage the head of the pin, whereuponupward movement of the shaft 125 draws the pin up free of the carriage.The head 130 is then rotated, by means of the shaft 125, through 90° tobring the pin precisely over the aperture 32 in the lid of thecontainer. Depression of the shaft 125 should then insert the pin,guided by means of the guide peg 129, into the aperture in thecontainer.

Attached to the lower end of the other shaft 126 is a second arm 132carrying a stripper pin 133. During the above described operation of thepick and place arm 130, the stripper pin arm is fully retracted andpivoted to the position shown in FIG. 13 at 132'. When the pick andplace arm has inserted the pin into the aperture of the container, thestripper pin arm 132 is rotated by means of the shaft 126 to bring thestripper pin 133 into alignment with the head of the current collectorpin held in the jaws of the pick up arm 130. The stripper pin 133 isthen depressed, by axial movement of the shaft 126 so as to engage thehead of the current collector pin and push the head out of the jaws ofthe pick and place arm 130, and firmly home to bear against the lid ofthe sodium container.

The stripper pin is then withdrawn from the pick and place arm androtated away again to the position 132'.

Referring again to FIG. 11, the rail 70 carrying the carriage 11 isitself mounted on an intermediate support frame 140 which is verticallymovable relative to the frame 124 within the chamber 2. The intermediatesupport frame 140 carrying the rail 70 and the carriage 11 can be raisedin its entirety by vertical axial movement of supporting shafts 141which extend through axial seals in the outer wall 142 of the fillingchamber 2. The construction of this lifting mechanism is illustrated inmore detail in FIGS. 14 and 15. The two supporting shafts 141 areactuated by means of cams 143 acting on cam follower rollers 144 mountedon the lower ends of the shafts 141 extending outside the wall 142 ofthe pressure vessel. The cams 143 are mounted on a shaft 145 extendinglongitudinally underneath the cylindrical pressure vessel. Rotation ofthe shaft 145 by means of a pneumatic cylinder acting on a lever 146rotates the cams 143 to raise and lower the supporting shafts 141, inturn raising and lowering the frame 140 with rail 70 carrying thecarriage 11.

Referring again to FIG. 11, the raising and lowering operation of thecarriage 11 enables individual sodium containers to be brought intoengagement with the filling head 121, pin insertion head 122 and weldinghead 123 as required.

Thus, when the carriage is to be driven along the rail 70 to bring afresh container into position under one of the heads 121, 122 and 123,the carriage is maintained in the lowered position. Once the containeris correctly positioned relative to the head, the carriage is lifted, bymeans of the cams 143, and shafts 141, to bring the container intoengagement with the head as required.

It will be appreciated that accurate positioning of each sodiumcontainer relative to the heads 121, 122 and 123 is essential. For thispurpose, locating pins 150, 151 are provided in the filling chamber 2which are axially movable to engage in the apertures 51 (FIG. 3) in theplatform 43 of the carriage 11. Thus, the carriage is first driven toapproximately the desired position presenting the intended containerimmediately beneath one of the heads 121, 122 and 123, and then thelocating pins 150 and 151 are driven upwards to engage firmly in one ormore of the apertures 51 of the carriage, thereby positively locatingthe carriage in the correct position for engagement of the selectedcontainer with the required head.

FIGS. 16 and 17 illustrate the operating mechanism for the locating pins150, 151. Each index pin 150, 151 of FIG. 11 (only pin 150 is shown inFIGS. 16 and 17 but the description applies equally to both locatingpins 150 and 151) is mounted for axial movement in a bearing 152 securedin a frame member 153 which is fixed within the chamber 2. The lower endof each pin 150 is journalled to one end of a lever arm 154 having itsother end keyed to a shaft 155. The shaft 155 interconnects the levers154 for both locating pins 150 and 151 and the shaft 155 is itselfpivoted between bearings 156 fixed within the chamber 2. A furtheractuating lever 157 is keyed to the shaft 155 midway between the levers154 and this lever 157 is connected via a piston rod 158 extending bymeans of an axial seal through the wall 142 of the chamber 2, to apneumatic cylinder 159.

Thus, operation of the pneumatic cylinder 159 to move the piston rod 158upwards in FIG. 17, rotates the shaft 155, thereby moving the locatingpins 150, 151 axially upwards also.

FIG. 17 illustrates in cross-section the platform 43 of the carriage 11showing in particular the aperture 51 into which one of the locatingpins 150, 151 can be inserted. It should be noted that apertures 160through the rail 70 are provided also immediately opposite each locatingpin 150, 151, to allow the pin to pass through the rail before engagingin aperture 51.

An operating procedure for use with the above apparatus illustrated inthe accompanying drawings will now be described referring to FIG. 18which is a schematic diagram of the vacuum system employed forindependently controlling the atmosphere in each of the three chambersof the apparatus, and constituting the separate systems illustrated at18, 19 and 20 in FIG. 1. It should be understood that all functions ofthe apparatus may be controlled remotely from control unit 27 which mayinclude a programmable controller for automating the procedure.

Firstly, a carriage such as illustrated in FIGS. 2 and 3 is loaded withsodium containers and current collector pins as described previously.Before entrance hatch 6 to the entry chamber is opened, the entrychamber is equalised to atmospheric pressure by opening valve V7 (bymeans of the control unit 27). When the pressure is equalised, andprovided the entry door 4 to the filling chamber 2 is clamped closed,hatch release push buttons are enabled by the control unit 27 to unlockhatch 6 so it can be opened. The carriage 11 carrying the sodiumcontainers is then introduced into the track system in the entry chamberand drawn fully into the chamber as described previously.

As mentioned before, the central container position on the carriage hasa dummy sodium container fitted with temperature sensors and when thecarriage has been fully drawn into the entry chamber, solenoid operatedswitch contacts connect this temperature sensor to the control unit 27.These switch contacts are formed, in the preferred embodiment, as aweighted arm pivoted in the entry chamber and having resilient contactfingers positioned to engage the aforementioned contact pads on theunderside of the platform 43 of the carriage. When the carriage is beingdriven into position in the chamber the arm is held pivoted away fromthe contact position by means of a solenoid. When the carriage is in thecorrect position, the solenoid can be de-energised, allowing theweighted arm to swing down pressing the contact fingers on to thecontact pads.

When the hatch 6 is subsequently closed and locked, the heaters 16 inthe entry chamber are energised to begin bringing the temperature of thesodium containers up to the desired say 150° C. At the same time, valveV7 is closed and the chamber is evacuated via valve V1 and pump RP1 to apressure of 1×10⁻² mbarAbs. Following evacuation, the entry chamber maybe flushed with argon gas by opening valve V8 and returned to a pressureof about 1 barAbs.

The chamber is then maintained at this pressure of argon and at thedesired temperature of 150° until the filling chamber is ready for thenext load.

When the filling chamber is available, it will have already discharged aprevious batch of filled containers to the exit chamber and will itselfbe at a pressure slightly in excess of 1 barAbs argon and at atemperature of 150° C.

The entry door clamps can then be released, under control from thecontrol unit 27, provided of course that the control unit detects thatthe entry hatch is locked shut. Because the pressure in the fillingchamber is slightly above that in the entry chamber, the closure memberof the door 4 is pushed away from its seating on releasing of the doorclamps and can then be slid open.

The heaters in the entry chamber are then switched off and thetemperature sensor in the dummy container is disconnect by energisingthe solenoid to draw back the weighted arm. The drive in the entrychamber is then engaged to drive the carriage forward through thedoorway engaging on the drive in the filling chamber which in turnoperates to draw the carriage fully into the filling chamber. When thecarriage is fully into the filling chamber 2, the entry door 4 is closedagain and clamped in position. During the period whilst the carriage waswaiting in the entry chamber, pump RP1 may have been called to evacuatethe exit chamber, whereupon valve V1 is closed and the pressure in theentry chamber is subsequently maintained by opening valve V5 andoperating pump RP2. Once the entry door 4 is closed again havingdelivered the carriage into the filling chamber, valve V5 is closed andthe vent valve V7 is opened again to allow the entry chamber to returnto atmospheric pressure for receipt of the next carriage.

In the filling chamber 2, the temperature sensor in the dummy containeris connected up so that the temperature of the containers can bemonitored throughout. As for the entry chamber, the contacts for thesensor are provided on a weighted arm and are released to make contactby de-energising a solenoid. However, in the filling chamber, theweighted arm is mounted so as to be slidable along a rail within thechamber, parallel to the direction of movement of the carriage. Anadditional finger on the weighted arm engages in a slot provided in theunderside of the platform 43 of the carriage so that when the arm isreleased for the fingers to engage the contact pads, the additionalfinger engages in the slot, whereby subsequent movement of the carriagedrags the arm sliding along its rail. A coiled lead connects to the armto provide electrical lead outs and so connection can be retained to thetemperature sensor continuously as the carriage is driven to and fro inthe chamber.

The gas pressure in the filling chamber 2 is maintained by pump RP2 viavalves V4 and V6. The drive in the entry chamber brings the carriage topresent the first container to the filling head and the location pins(150, 151 from FIG. 11) are operated to correctly locate the firstcontainer. The carriage is then raised (as described with reference toFIGS. 14 and 15) so that the filling nozzle of the sodium filling headis inserted into the aperture in the lid of the first container. Thefilling head then injects a first quantity of liquid sodium into thefirst cell.

Thereafter the carriage is lowered, location pins 150 and 151 areretracted, and the drive means operates to move the carriage forward tothe next container whereupon the filling procedure is repeated for thesecond container. When all ten containers have received a first volumeof molten sodium, the control unit causes the chamber to be evacuated to1×10⁻¹ mbarAbs using booster pump MB1 and backing pump RP1 with valve V6closed and valves V4 and V2 open. The filling chamber is thenrepressurised with argon by opening valve V9 to bring the pressure backup to 1 bar.

This procedure is necessary to force the sodium within the sodiumcontainers into the particulate aluminium filler gettering agent withinthe container. Sufficient sodium may be delivered so that theparticulate aluminium, which may be in the form of powder or flakes, isfully covered on repressurising. The filling procedure is then repeatedonce more for each of the ten containers to introduce a further quantityof sodium into each container to top the container up. Generally, thefurther quantity will be less than that initially introduced.

On completion of the final filling operation, valve V4 and V2 are openedagain and pumps MB1 and RP2 reduce the pressure in the filling chamberto 880 mbarAbs whereupon valve V4 and V2 are again closed. The carriageis then driven to bring the first container under the pin insertion head14 (FIG. 1) and again the locating pins are actuated so as properly tolocate the carriage in position. The carriage is then raised as beforeand the pin insertion head is operated to insert the current collectorpin into the first container on the carriage.

Subsequently, the carriage is lowered again and driven forward to repeatthe process on the second container in the carriage.

When the pin is being inserted in the fourth container on the carriage,the first container, with pin already inserted, will be directly beneaththe welding head 15 (FIG. 1) so that welding of the first container cantake place simultaneously with pin insertion on the fourth container.

The welding and pin insertion actions continue for each container inturn along the carriage, skipping the dummy container in the middle,until the pin has been inserted in the tenth container, simultaneouslywith welding the seventh container. Thereafter the eighth, ninth andtenth containers are in turn presented to the welding head to completethe welding and sealing of all the containers.

All ten containers should then be filled with sodium and properly sealedthis having been done in an atmosphere of 880 mbarAbs argon at atemperature of 150° C. When all containers are completed, the carriageis returned to the initial position where the temperature sensor isdisconnected. Then, the heaters 17 in the filling chamber 2 are switchedoff and when the exit chamber 3 is ready, the carriage is driven forwardtowards the exit door 5. When the pressure in the exit chamber is justbelow 880 mbarAbs, and provided the exit hatch 7 is locked shut, theexit door 5 can be unclamped and opened. Then the carriage is drivenforward from the filling chamber to engage in the drive 10 in the exitchamber which draws the carriage fully into the exit chamber, whereuponthe door 5 is closed and clamped again and the filling chamber 2 isimmediately ready to receive a fresh carriage from the entry chamber.

In the exit chamber, the temperature sensor in the dummy container isagain connected so that the temperature of the containers can bemonitored as they cool. Once the containers have cooled down to apredetermined value, the pressure in the exit chamber is equalised withatmospheric by opening vent valve V10 to air. The temperature sensor inthe dummy container is then disconnected and the locks on the exit hatch7 may be released, provided the control unit detects that the exit door5 is clamped shut. When the hatch 7 is open, the carriage with filledand sealed containers thereon can be removed for unloading and furtherprocessing.

The exit chamber hatch 7 is then shut and locked, the vent valve V1Oclosed and valve V3 opened so that pump RP1 can reduce the pressure inthe exit chamber to 1×10⁻¹ mbarAbs. Thereafter, valve V3 is shut andvalve V11 opened to flush the exit chamber with argon gas up to apressure of 880 mbarAbs. The exit chamber is then again ready to receivea freshly processed batch of containers from the filling chamber.

We claim:
 1. Apparatus for filling and sealing an alkali metal containerfor an alkali metal energy conversion device, comprisingintercommunicating entry, filling and exit chambers, entry and exitdoors which are closable to hermetically seal the filling chamber fromthe entry and exit chambers respectively, hermetically sealable entryand exit hatches to the entry and exit chambers respectively, interlockmeans to permit opening of said entry or exit hatch only when therespective said entry or exit door is closed, transfer means operable totransfer an alkali metal container to be filled and sealed successivelyfrom the entry chamber to the filling chamber and, when filled andsealed, from the filling chamber to the exit chamber, vacuum meansarranged for independently controlling the atmosphere in each of theentry, filling and exit chambers to provide a respective pressure ofinert gas in each of said changers, heating means arranged forindependently controlling the temperatures in at least said entry andfilling chambers, and filling and sealing means arranged to fill saidcontainer with molten alkali metal and seal said container in thefilling chamber, the said transfer means comprising a carriage arrangedto hold at least one said electrode container, and respective drivemeans in each of said chambers for guiding and propelling the carriagein the respective chamber, the respective drive means in adjacentcommunicating chambers being adapted to co-operate in supporting andpropelling the carriage from one said chamber to the next through theopen door between the chambers, the carriage having sufficient length inthe direction of transfer to ensure full guided supporting engagementwith one drive means is retained during transfer at least until thecarriage engages the next drive means.
 2. Apparatus as claimed in claim1, wherein each drive means is adapted to provide cantilever support forthe carriage during transfer, until engagement with a following drivemeans and after disengagement from a preceding drive means.
 3. Apparatusas claimed in claim 1 wherein the drive means in the filling chamberincludes a length of rail for engagement on opposite sides of the railby opposed pairs of rollers on the carriage, the end of the railadjacent the entry door being tapered to facilitate engagement of therail between said pairs of rollers during transfer.
 4. Apparatus asclaimed in claim 3 wherein the opposed pairs of rollers are arranged tosubstantially restrict the movement of the carriage in a directionperpendicular to the axis of the drive means.
 5. Apparatus as claimed inclaim 1 wherein the carriage is adapted to hold said electrode containerat a position on the carriage and the drive means in the filling chamberis arranged to convey the electrode container on the carriage betweenrespective filling and sealing stations within the filling chamber, theapparatus including inter-engagable locating means on the carriage andin the filling chamber actuatable to locate the electrode containeraccurately relative to the filling and sealing means in the filling andsealing stations respectively.
 6. Apparatus as claimed claim 5, whereinsaid inter-engagable locating means comprise a locating pin mountedeither on the carriage or in the filling chamber to be longitudinallymovable on actuation to engage in a corresponding aperture in thefilling chamber or in the carriage respectively.
 7. Apparatus as claimedin claim 6, wherein at least one of the locating pin and said apertureis tapered to assist positive engagement between the pin and aperture.8. Apparatus as claimed in claim 6 wherein there is a single saidlocating pin and a respective said corresponding aperture for each ofthe filling and sealing stations.
 9. Apparatus as claimed in claim 6wherein there are at least two locating pins mounted in the fillingchamber arranged for engaging successively in a common aperture in thecarriage to locate the electrode container firstly at the fillingstations and secondly at the sealing station.
 10. Apparatus as claimedin claim 1, and including guide means in the filling chamber forsupporting and guiding the electrode container between respectivefilling and sealing stations in the filling chamber, and lifting meansactuatable to lift the guide means and the electrode chamber supportedthereon into operative engagement with the filling and sealing means.11. Method of filling alkali metal electrode containers, for alkalimetal energy conversion devices, each container holding solid material,with molten alkali metal having a large wetting angle to the solidmaterial, comprising the steps of filling said container with gas whichis inert to the alkali metal; pumping a first quantity of the moltenalkali metal into the container; reducing the pressure of said gas inthe container and then raising the pressure of the gas to increase thewetting of the solid material by the molten alkali metal.
 12. Method asclaimed in claim 11 wherein the container is initially filled with saidgas at a particular pressure, and after said pressure reducing step, thepressure is raised again to said particular pressure.
 13. Method asclaimed in claim 11 comprising the further step of pumping a secondquantity of alkali metal into the container after the gas pressure israised again.
 14. Method as claimed in claim 11 wherein the solidmaterial is a gettering agent.
 15. Method as claimed in claim 14 whereinthe gettering agent is aluminium powder or flakes.
 16. Method as claimedin claim 11 wherein the first quantity of alkali metal is sufficient tofully cover the solid material, on raising the pressure of the gas. 17.Method as claimed in claim 13 wherein the first quantity of alkali metalexceeds the second quantity of alkali metal.
 18. Method as claimed inclaims 11 wherein the container is positioned inside a pressure chamberfilled with said gas.
 19. Method as claimed in claim 18 wherein varyingthe pressure of the gas in the container is effected by varying thepressure of the gas in the pressure chamber.